Decorative laminate incorporating photoluminescent material

ABSTRACT

A decorative laminate is provided which is comprised of a one or more cellulosic core sheets, one or more decor sheets and optional overlay sheets. In one embodiment, one or more of the overlay sheets and/or decor sheets are impregnated prior to lamination with a mixture of a transparent resin and a photoluminescent material. As a result, the entire upper surface of the laminate visibly luminesces in the presence of exciting radiation. In another embodiment, an image or pattern is printed on one or more of the decor sheets with a ink including an organic photoluminescent material to provide an visibly luminescent image or pattern therein. It is envisioned that the invention could be used to provide a unique and appealing appearance when used as the surfacing for a wide variety of applications, including bowling lanes, game tables, counter-tops, dance floors, and signs such as “exit” signs.

RELATED APPLICATION

This application is claiming the benefit, under 35 USC §119(e), of theprovisional application filed Jun. 28, 1996 under 35 USC §111(b), whichwas granted a serial number of 60/020,751. The provisional application,Ser. No. 60/020,751, is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

This invention relates generally to decorative laminates formed of aplurality of resin impregnated cellulosic sheets. More particularly,this invention relates to high pressure decorative laminates whichincorporate a material which is visibly luminescent upon exposure toultraviolet light, and to methods of producing the same.

BACKGROUND OF THE INVENTION

Conventionally, high pressure decorative laminates are made of twoessential layers: a core layer and a surface layer. The core layerconstitutes a bottom or supporting layer onto which the other layer isbonded. In normal high-pressure laminate manufacture, the core layerconsists of a plurality of cellulosic sheets. The core sheets aregenerally made from a kraft paper impregnated with a laminating resin.Laminating resins commonly used for the core layer include phenolic,melamine, amino, epoxy, polyester, silicone, and diallyl phthalateresins to name a few. The industrially preferred laminating resin fordecorative laminates is a phenolic resin made from the reaction ofphenols with formaldehyde.

Placed above the core layer is a decorative layer which is generallyformed of one or more sheets of cellulose pigmented paper containing aprint, pattern design or solid color that has been impregnated with atransparent resin, such as melamine, amino, epoxy, polyester, silicone,and diallyl phthalate resins to name a few. The preferred and typicallyused resin for the papers of the decorative layer ismelamine-formaldehyde resin. The cured melamine-formaldehyde resins arecolorless, resistant to light and heat, as well as being resistant to avariety of solvents and stains.

When the decorative layer of the laminate includes a printed pattern, itis commonly covered with what is generally referred to as an overlay,which is typically a high-quality alpha cellulose paper impregnated witha melamine-formaldehyde resin. This layer protects the decorative printfrom external abuse such as abrasive wear and tear, harsh chemicals,burns, spills and the like. It is primarily the melamine-formaldehyderesin which accounts for these protective properties of the laminate.The alpha-cellulose paper acts as a translucent carrier for thewater-thin resin, imparts strength to the melamine-formaldehyde resin,maintains a uniform resin thickness in the overlay by acting as a shim,and controls resin flow.

The core layer, decorative layer and the overlay surface layer (whenneeded) are stacked in a superimposed relationship, between steel pressplates and subjected to a pressure and temperature for a time sufficientto cure the laminating resins impregnating the respective layers. Theelevated temperature and pressure actually cause the impregnated resinswithin the sheets to flow, which consolidates the whole into an integralmass known as the laminate. These laminates are used as surfacings forfloors, counter tops, table tops, furniture, store fixtures, and thelike. Examples of conventional high pressure decorative. laminates aregiven, for example, in U.S. Pat. No. 3,418,189 to Grosheim et al., U.S.Pat. No. 4,311,748 to Casey et al., U.S. Pat. No. 4,473,613 to Jaisle etal., and U.S. Pat. No. 4,741,968 to Dion et al., each of which isincorporated herein by reference.

SUMMARY OF THE INVENTION

In accordance with the invention, a decorative laminate is providedwhich is comprised of a core layer, a decorative layer and an optionalsurface layer or overlay which are stacked and laminated under heat andpressure. The core layer includes one or more melamine or phenolic resinimpregnated sheets of kraft paper or the like; the decorative layerincludes one or more melamine impregnated printed sheets; and theoptional overlay includes one or more thin protective melamineimpregnated paper layers. In one embodiment of the invention, an imageor pattern is printed on one or more of the decorative paper layers witha ink including a photoluminescent material to provide an image orpattern therein which is visible when exposed to a source of ultravioletlight (i.e., a source of electromagnetic radiation in the range of about200-400 nm). The term “photoluminescent” is used herein to denote amaterial which is either visibly phosphorescent (i.e., where there is acontinued luminescent radiation after termination of the excitingradiation) or visibly fluorescent (i.e., where the luminescent radiationceases as soon as the exciting radiation is removed). The decorativepaper layers are then each saturated with a clear resin, such asmelamine-formaldehyde, and stacked with a core layer and, optionally,the overlay, and laminated under heat and pressure.

In a further embodiment, the photoluminescent material is visiblyphosphorescent after exposure to exciting radiation in the visiblerange.

In another embodiment, one or more of the overlay papers and/ordecorative layer papers are impregnated prior to lamination with amixture of a transparent resin, preferably melamine, and aphotoluminescent material. As a result, the entire upper surface of thelaminate visibly luminesces in the presence of ultraviolet light.

In a still further embodiment of the invention, one or more of thedecorative layer papers is saturated with a mixture of resin and aphotoluminescent material, or is provided with a design or patternprinted with an ink including a photoluminescent material, and is thenlow pressure laminated or thermofused to a substrate such as particleboard, fiber board or the like.

It is envisioned that the invention could be used to provide a uniqueand appealing appearance when used as the surfacing for a wide varietyof applications, including bowling lanes, game tables, counter-tops,dance floors, and signs such as “exit” signs. The invention could alsobe used to provide selectively viewable printed information, such asmanufacturer identifiers, for otherwise conventional decorative laminateapplications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is directed to decorative laminates which incorporate aphotoluminescent material. In a first embodiment of the invention, thedecorative laminate comprises a core layer, a decorative layer, andpreferably an overlay. The core layer is of known construction andconsists of one or more cellulosic sheets, preferably formed of a kraftpaper, impregnated with a laminating resin. Any of the conventionallaminating resins commonly used for the core layer, such as phenolic,melamine, amino, epoxy, polyester, silicone, and diallyl phthalateresins, to name a few, may be used. The preferred laminating resin is aphenolic resin made from the reaction of phenols with formaldehyde.

Placed above the core layer is a decorative layer which is formed of oneor more cellulosic sheets, preferably sheets of alpha cellulose paper.Using a printing composition including an effective amount of aphotoluminescent material, a design or pattern is applied to the surfaceof one or more of the cellulosic sheets forming the decorative layer. Itis generally preferable to apply the design or pattern to the sheet orsheets which, in the final laminate, will be positioned furthest fromthe core layer to enhance the intensity of the luminescent radiationemitted from the surface of the laminate. The design or pattern ispreferably applied to the outermost paper sheet or sheets. The manner inwhich the printing composition is applied to the sheet or sheets is notcritical, and any known printing method, such as screen printing,gravure printing or the like, may be used.

The printing composition used in accordance with the invention includesa photoluminescent material dispersed in a suitable vehicle which offersthe flow characteristics desired for the selected printing method. Thephotoluminescent material is provided in an amount which is effective tocause the printed design or pattern to be visibly luminescent in thefinal laminate. Many types of known ultraviolet light sensitive dyes orpigments may be used. In addition, visible light sensitivephosphorescent materials may also be used. Selection of a particular dyeor pigment will typically depend upon the desired color to be generatedwhen the material luminesces, and whether phosphorescence orfluorescence is desired for a given application. In addition, theselected photoluminescent dye or pigment must be able to withstand theheat and pressure to which the layers are exposed during the subsequentlamination process. One preferred photoluminescent material is LeucophorBCR™, available from Clariant Corp. of Charlotte, N.C. Leucophor BCR™ isa stilbene material supplied as a liquid having about 49% solids andwhich generates a blue color upon luminescence. Stilbene materials arepreferred.

The photoluminescent pigment or dye may be combined with conventionalprinting inks with which the selected photoluminescent pigment or dye iscompatible and can be readily dispersed. For example, thephotoluminescent pigment or dye may be combined with a Clear ScreenPrint Extender™, commercially available from Gotham Ink of Marlboro,Mass. Opaque colored pigments, such as brown or white, may optionally beincluded. Thus, depending upon the desired appearance of the finallaminate, the printing composition may include opaque colored(non-photoluminescent) pigments or dyes so that the image or pattern isvisible when under normal light conditions. However, thephotoluminescent effect may be reduced by the addition ofnon-photoluminescent pigments or dyes, especially darker coloredpigments or dyes, such as brown. Thus, the inclusion ofnon-photoluminescent pigments or dyes in the printing composition isgenerally not preferred, leaving the printing composition substantiallyclear under normal light conditions.

As will be appreciated by those skilled in the art, the printingcomposition may also include suitable amounts of other additives, suchas viscosity modifiers, heat stabilizers, wetting agents, binders or thelike, without departing from the scope of the invention.

In addition, it is contemplated that one or more of the decorativesheets may also be provided with a printed pattern or design with aconventional, non-photoluminescent ink composition. In this manner, thefinal laminate would exhibit a decorative surface with multiple patternsor designs, one set which is visible under normal light or daylightconditions, and another set which is visible in the presence ofultraviolet light.

Once the decorative sheet or sheets have been provided with the desiredpattern or design, each sheet is then impregnated with a transparentresin as is conventional. Examples of transparent resins includemelamine, polyester, acrylics, epoxy, amino, silicone, etc. Amelamine-formaldehyde resin is preferred.

Finally, an overlay of a cellulosic paper or papers impregnated with asuitable transparent resin is generally provided. High-quality alphacellulose paper(s) is preferred for the overlay. As with the decorativelayers, melamine-formaldehyde is the preferred impregnating resin. Ofcourse, the design or pattern of the photoluminescent printingcomposition could be printed on one of the sheets which may be termedone of the “overlay” papers. In this case, it is preferable that theprinting be applied to the overlay paper(s) nearest the core anddecorative layers.

The core layer, decorative layer and the optional overlay surface layerare stacked in a superimposed relationship between steel press plates orthe like. As will be appreciated by those skilled in the art, anadditional decorative layer and optional overlay may be provided on theopposite face of the core layer, resulting in a laminate in which bothmajor surfaces are decorative. As is well known in the art, the stackedlayers are subjected to a sufficient pressure and temperature, and for atime sufficiently long, to cure the laminating resins impregnating therespective layers. The laminating temperature is at least about 230° F.,and is usually in the range of about 250° F. to about 300° F. Thepressure is generally increased to between about 305 to 1500 psi. Theelevated temperature and pressure cause the impregnated resins withineach of the sheets to flow, which consolidates the whole into anintegral mass known as the laminate.

When a source of ultraviolet light is provided, it penetrates theoverlay and impinges upon the decorative layers. As a result, thephotoluminescent material printed on the sheets comprising thedecorative layer is caused to emit luminescent radiation so that theprinted design or pattern is visible. Depending upon thephotoluminescent material used, the amount of such material used, theintensity of the source of ultraviolet light, and the color of thebackground, it may be necessary to reduce the level of visible lightimpinging upon the laminate to enhance the visibility of the luminescentdesign or pattern.

In an alternate embodiment of the invention, the printing compositionincluding an effective amount of a photoluminescent material is appliedto the entire surface of one or more of the cellulosic sheets formingthe decorative layer. Any conventional printing technique may beemployed. In this manner, the entire treated surface of the resultinglaminate may be made to emit visible luminescent radiation in thepresence of ultraviolet light.

In a further embodiment of the invention, a similar result is obtainedwherein a mixture of the selected transparent resin, preferablymelamine-formaldehyde, and a photoluminescent material is prepared. Thephotoluminescent material may be any of the suitable known materials asdiscussed above. One or more of the overlay papers and/or the decorativelayer papers is impregnated with the resulting mixture of resin andphotoluminescent material in the conventional manner. The core layer,decorative layer and the optional overlay surface layer are stacked in asuperimposed relationship and subjected to a pressure and temperature aswith the known high pressure decorative laminates. Again, as a result,the entire upper surface of the laminate would be luminescent in thepresence of ultraviolet light.

In addition, in the case where a photoluminescent material is applied tosubstantially the entirety of one or more of the overlay papers and/orthe decorative layer papers, another one or more of such papers mayoptionally be provided with an image, design or pattern printed with anopaque ink. The paper to which the opaque printing is applied would bepositioned nearer the outer surface of the final laminate than the paperor papers to which the photoluminescent material is applied. As aresult, in the presence of ultraviolet light, the entire upper surfaceof the laminate would be luminescent except for those portionscorresponding to the image, design or pattern printed with an opaqueink, creating a “negative” image.

In still another embodiment of the invention, one or more of the overlaypapers and/or the decorative layer papers are prepared as discussedabove, with either printing or saturation with a photoluminescentmaterial. The so-treated papers are then incorporated into a lowpressure laminate. The papers treated with the photoluminescent materialare stacked in a superimposed relationship with a rigid substrate, suchas particle board, fiber board or the like. If printing is applied toone or more of the papers, an overlay is preferably included asdiscussed above. Each of the paper layers is impregnated with a resin inthe same manner as for the high pressure laminates discussed above,although typically, as appreciated by those skilled in the art, a highercatalyst level is employed with a low pressure or thermofused laminate.A melamine-formaldehyde resin is preferred. All of these layers areplaced in a hot press between steel press plates and subjected to arelatively low pressure and temperature for a time sufficiently longenough to cure the laminating resins impregnating the respective layers,as is conventional.

It is further contemplated that photochromic dyes could be used in placeof or in conjunction with the photoluminescent materials in any of theapplications discussed above. A photochromic dye is one which reflectsone color in the visible spectrum when in the presence of light of afirst wavelength, such as visible light, and reflects a second differentcolor in the visible spectrum when in the presence of light of adifferent, second wavelength such as ultraviolet light.

The following examples are illustrative of the present invention and donot constitute any limitation with regard to the subject matter of theinvention.

EXAMPLE 1

A solution was prepared using 3000.0 gms of Clear Screen PrintExtender™, available from Gotham Ink of Marlboro, Mass., at 50% solidswith 161.1 gms of Leucophor BCR™, available from Clariant Corp., at 49%solids. The resulting solution was Clear Screen Print Extender™ withapproximately 5% Leucophor BCR based on solids. This solution was screenprinted in a pattern onto multiple cellulose paper sheets previouslyprovided with a maple grain design. These sheets were impregnated withmelamine-formaldehyde resin prior to printing.

Two laminates were produced, each having the following layers stacked ina superimposed relationship as follows: one light basis weightmelamine-formaldehyde impregnated overlay sheet, two high wear overlaymelamine-formaldehyde impregnated sheets, one of the above mentionedscreen printed melamine-formaldehyde impregnated decorative sheets,forty six phenolic impregnated kraft paper core sheets (for bulk andstrength), one melamine-formaldehyde impregnated balance sheet (to helpprevent warpage), two high wear overlay melamine-formaldehydeimpregnated sheets, and one light basis weight melamine-formaldehydeimpregnated overlay sheet. The sheets were positioned between steelpress plates and subjected to about 1200 psi at a maximum temperature ofabout 300° F. for a total time of about 35 minutes.

The patterns screen printed with the solution of Clear Screen PrintExtender™ with Leucophor BCR were difficult to see under normallighting, but exhibited excellent fluorescence when exposed to a sourceof ultraviolet light.

EXAMPLE 2

The following resin formulation was prepared by blending in a 5 gallonvessel:

Component Amount (gms) Weight % Piomel 110¹ 18359.4 91.80 Water 602.53.01 Hypersal² 26.6 0.13 Magnesium Chloride 12.1 0.06 Leucophor BCR1000.0 5.00

1. A melamine-formaldehyde resin available from Pioneer PlasticsCorporation of Auburn, Me.

2. A wetting agent available from Hoechst Celanese.

Overlay sheets (22# basis weight alpha cellulose paper) were impregnatedwith a mixture of the above formulation to a resin content of 69% byweight. A series of 3 laminates was prepared, each having onemelamine-formaldehyde impregnated maple grain decorative sheet, tenphenolic impregnated kraft paper core sheets, one melamine-formaldehydeimpregnated balance sheet, two high wear overlay melamine-formaldehydeimpregnated sheets, and one light basis weight melamine-formaldehydeimpregnated overlay sheet. Each of the 3 laminates was provided with adifferent top face construction as follows:

(1) one 22# basis weight melamine-formaldehyde impregnated overlay sheet

one overlay sheet impregnated with the above resin/fluorescentformulation

one 22# basis weight melamine-formaldehyde impregnated overlay sheet

(2) two 22# basis weight melamine-formaldehyde impregnated overlaysheets

one overlay sheet impregnated with the above resin/fluorescentformulation

(3) one 22# basis weight melamine-formaldehyde impregnated overlaysheets

two overlay sheet impregnated with the above resin/fluorescentformulation

In each case, the sheets were positioned between steel press plates andsubjected to about 1200 psi at a maximum temperature of about 300° F.for a total time of about 35 minutes.

All three laminates exhibited visible fluorescence when exposed to asource of ultraviolet light. Under the same ultraviolet light source,the laminate (3) showed the highest intensity of fluorescence.

EXAMPLE 3

Three samples were prepared as in Example 1, except that the LeucophorBCR™ was replaced with a phosphorescent metal oxide pigment LuminovaG300C, commercially available from United Mineral & Chemical Corporationof Lyndhurst, N.J. The three samples were prepared using 1, 2 and 5weight percent, respectively, of the Luminova G300C, and were laminatedas in Example 1. Each of the three samples exhibited a visiblephosphorescent “glow” in a darkened room after exposure to visiblelight.

EXAMPLE 4

A resin formulation was prepared as in Example 2, with the 0.5 weightpercent of Day Glow D-282 powder used in place of the 5 weight percentLeucophor BCR™. The Day Glow D-282 is composed of organic resinparticles containing dyes which are capable of fluorescing while in asolid state solution, and are commercially available from Day-Glo ColorCorp. of Cleveland, Ohio. The samples were prepared as in Example 2, andthe resulting laminates exhibited a high intensity of fluorescence.

In accordance with the provisions of the patent statutes, the inventionhas been described in what is considered to represent its preferredembodiments. However, it should be noted that the invention can bepracticed otherwise than as specifically illustrated and describedwithout departing from its spirit or scope.

What we claim is:
 1. A heat add pressure consolidated decorativelaminate comprising: a core layer including one or more cellulosicsheets impregnated with a thermosetting resin; a decorative layerincluding one or more cellulosic sheets impregnated with a transparentthermosetting resin; and an optional overlay including one or morecellulosic sheets impregnated with a transparent thermosetting resin;wherein a photoluminescent material is applied by impregnation tosubstantially the entirety of a selected one or more sheets of saiddecorative layer or said overlay or both thereby saturating saidselected one or more sheets with said photoluminescent material.
 2. Adecorative laminate as defined in claim 1, wherein said selected one ormore sheets is impregnated with a mixture of said resin and saidphotoluminescent material.
 3. A decorative laminate as defined in claim1, wherein a selected one or more sheets of said decorative layer orsaid overlay or both is provided with an image, design or patternprinted with an opaque ink.
 4. A decorative laminate as defined in claim1, wherein said one or more sheets of said decorative layer areimpregnated with a thermosetting melamine/formaldehyde reaction product.5. A decorative laminate as defined in claim 1, wherein said one or moresheets of said core layer are impregnated with a thermosettingphenol/formaldehyde reaction product.
 6. A decorative laminate asdefined in claim 1, wherein said overlay is provided and said one ormore sheets thereof are impregnated with a thermosettingmelamine/formaldehyde reaction product.
 7. A decorative laminate asdefined in claim 1, wherein said photoluminescent material includes anorganic dye or pigment.
 8. A decorative laminate as defined in claim 1,wherein said photoluminescent material includes a stilbene material. 9.A decorative laminate as defined in claim 1, wherein saidphotoluminescent material is visibly phosphorescent after exposure toexciting radiation in the visible range.
 10. The decorative laminate asdefined in claim 1, wherein a selected one or more sheets of saiddecorative layer or said overlay or both is provided with an image,design or pattern printed with conventional, non-photoluminescent ink.11. A decorative laminate as defined in claim 10, wherein saidphotoluminescent material includes a stilbene material.
 12. A method offorming a heat and pressure consolidated decorative laminate comprising:a) impregnating one or more cellulosic core sheets with a thermosettingresin; b) providing one or more cellulosic decor sheets and, optionally,one or more cellulosic overlay sheets; c) impregnating a selected one ormore sheets, selected from said decor sheets and said optional overlaysheets, with a transparent thermosetting resin and a photoluminescentmaterial thereby saturating said selected one or more sheets with saidphotoluminescent material; d) impregnating any remaining decor sheetsand optional overlay sheets with a transparent thermosetting resin; e)forming a stacked assembly of said core sheets, said decor sheets andsaid optional overlay sheets; and f) heat and pressure consolidating theresultant assembly into a decorative laminate.
 13. A method as definedin claim 12, wherein said selected one or more sheets are impregnatedwith a mixture of said resin and said photoluminescent material.
 14. Amethod as defined in claim 12, further comprising the step of providingan opaque image, design or pattern on a selected one or more of saiddecor sheets.
 15. A method as defined in claim 12, wherein said one ormore decor sheets are impregnated with a thermosettingmelamine/formaldehyde reaction product.
 16. A method as defined in claim12, wherein said one or more core sheets are impregnated with athermosetting phenol/formaldehyde reaction product.
 17. A method asdefined in claim 12, wherein one or more overlay sheets are provided andsaid one or more overlay sheets are impregnated with a thermosettingmelamine/formaldehyde reaction product.
 18. A method as defined in claim12, wherein said photoluminescent material includes an organic dye orpigment.
 19. A method as defined in claim 18, wherein saidphotoluminescent material includes a stilbene material.
 20. A method asdefined in claim 12, wherein said photoluminescent material is visiblyphosphorescent after exposure to exciting radiation in the visiblerange.